added slides for getting started with functions.
#+LaTeX_CLASS: beamer
#+LaTeX_CLASS_OPTIONS: [presentation]
#+BEAMER_FRAME_LEVEL: 1
#+BEAMER_HEADER_EXTRA: \usetheme{Warsaw}\usecolortheme{default}\useoutertheme{infolines}\setbeamercovered{transparent}
#+COLUMNS: %45ITEM %10BEAMER_env(Env) %10BEAMER_envargs(Env Args) %4BEAMER_col(Col) %8BEAMER_extra(Extra)
#+PROPERTY: BEAMER_col_ALL 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 :ETC
#+LaTeX_CLASS: beamer
#+LaTeX_CLASS_OPTIONS: [presentation]
#+LaTeX_HEADER: \usepackage[english]{babel} \usepackage{ae,aecompl}
#+LaTeX_HEADER: \usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}
#+LaTeX_HEADER: \usepackage{listings}
#+LaTeX_HEADER:\lstset{language=Python, basicstyle=\ttfamily\bfseries,
#+LaTeX_HEADER: commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
#+LaTeX_HEADER: showstringspaces=false, keywordstyle=\color{blue}\bfseries}
#+TITLE: Getting started with functions
#+AUTHOR: FOSSEE
#+EMAIL: info@fossee.in
#+DATE:
#+DESCRIPTION:
#+KEYWORDS:
#+LANGUAGE: en
#+OPTIONS: H:3 num:nil toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
#+OPTIONS: TeX:t LaTeX:nil skip:nil d:nil todo:nil pri:nil tags:not-in-toc
# * Outline
# - Manipulating one and multi dimensional arrays
# - Access and change individual elements
# - Access and change rows and columns
# - Slicing and striding on arrays to access chunks
# - Read images into arrays and manipulations
# * Sample Arrays
# #+begin_src python
# In []: A = array([12, 23, 34, 45, 56])
# In []: C = array([[11, 12, 13, 14, 15],
# [21, 22, 23, 24, 25],
# [31, 32, 33, 34, 35],
# [41, 42, 43, 44, 45],
# [51, 52, 53, 54, 55]])
# #+end_src
# * Question 1
# Change the last column of ~C~ to zeroes.
# * Solution 1
# #+begin_src python
# In []: C[:, -1] = 0
# #+end_src
# * Question 2
# Change ~A~ to ~[11, 12, 13, 14, 15]~.
# * Solution 2
# #+begin_src python
# In []: A[:] = [11, 12, 13, 14, 15]
# #+end_src
# * squares.png
# #+begin_latex
# \begin{center}
# \includegraphics[scale=0.6]{squares}
# \end{center}
# #+end_latex
# * Question 3
# - obtain ~[22, 23]~ from ~C~.
# - obtain ~[11, 21, 31, 41]~ from ~C~.
# - obtain ~[21, 31, 41, 0]~.
# * Solution 3
# #+begin_src python
# In []: C[1, 1:3]
# In []: C[0:4, 0]
# In []: C[1:5, 0]
# #+end_src
# * Question 4
# Obtain ~[[23, 24], [33, -34]]~ from ~C~
# * Solution 4
# #+begin_src python
# In []: C[1:3, 2:4]
# #+end_src
# * Question 5
# Obtain the square in the center of the image
# * Solution 5
# #+begin_src python
# In []: imshow(I[75:225, 75:225])
# #+end_src
# * Question 6
# Obtain the following
# #+begin_src python
# [[12, 0], [42, 0]]
# [[12, 13, 14], [0, 0, 0]]
# #+end_src
# * Solution 6
# #+begin_src python
# In []: C[::3, 1::3]
# In []: C[::4, 1:4]
# #+end_src
# * Summary
# You should now be able to --
# - Manipulate 1D \& Multi dimensional arrays
# - Access and change individual elements
# - Access and change rows and columns
# - Slice and stride on arrays
# - Read images into arrays and manipulate them.
* Outline
- Define functions
- Pass arguments to functions
- Learn about docstrings
- Return values from functions
* Function
- Eliminate code redundancy
- Help in code reuse
- Subroutine
- relatively independent of remaining code
* ~f(x)~ a mathematical function
$f(x) = x^{2}$
: f(1) -> 1
: f(2) -> 4
* Define ~f(x)~ in Python
#+begin_src python
def f(x):
return x*x
#+end_src
- ~def~ - keyword
- ~f~ - function name
- ~x~ - parameter / argument to function ~f~
* Exercise 1
Write a python function named ~cube~ which computes the cube of a given
number ~n~.
- Pause here and try to solve the problem yourself.
* Solution
#+begin_src python
def cube(n):
return n**3
#+end_src
* ~greet~ function
Function ~greet~ which will print ~Hello World!~.
#+begin_src python
def greet():
print "Hello World!"
#+end_src
- Call the function ~greet~
: In []: greet()
: Hello World!
* Exercise 2
Write a python function named ~avg~ which computes the average of
~a~ and ~b~.
- Pause here and try to solve the problem yourself.
* Solution 2
#+begin_src python
def avg(a,b):
return (a + b)/2
#+end_src
- ~a~ and ~b~ are parameters
- ~def f(p1, p2, p3, ... , pn)~
* Docstring
- Documenting/commenting code is a good practice
#+begin_src python
def avg(a,b):
""" avg takes two numbers as input
(a & b), and returns the average
of a and b"""
return (a+b)/2
#+end_src
- Docstring
- written in the line after the ~def~ line.
- Inside triple quote.
- Documentation
: avg?
* Exercise 3
Add docstring to the function f.
* Solution 3
#+begin_src python
def f(x):
"""Accepts a number x as argument and,
returns the square of the number x."""
return x*x
#+end_src
* Exercise 4
Write a python function named ~circle~ which returns the area and
perimeter of a circle given radius ~r~.
* Solution 4
#+begin_src python
def circle(r):
"""returns area and perimeter of a circle given
radius r"""
pi = 3.14
area = pi * r * r
perimeter = 2 * pi * r
return area, perimeter
#+end_src
* ~what~
#+begin_src python
def what( n ):
if n < 0: n = -n
while n > 0:
if n % 2 == 1:
return False
n /= 10
return True
#+end_src
* ~even_digits~
#+begin_src python
def even_digits( n ):
"""returns True if all the digits of number
n is even returns False if all the digits
of number n is not even"""
if n < 0: n = -n
while n > 0:
if n % 2 == 1:
return False
n /= 10
return True
#+end_src
* ~what~
#+begin_src python
def what( n ):
i = 1
while i * i < n:
i += 1
return i * i == n, i
#+end_src
* ~is_perfect_square~
#+begin_src python
def is_perfect_square( n ):
"""returns True and square root of n,
if n is a perfect square, otherwise
returns False and the square root
of the next perfect square"""
i = 1
while i * i < n:
i += 1
return i * i == n, i
#+end_src
* Summary
- Functions in Python
- Passing parameters to a function
- Returning values from a function
- We also did few code reading exercises.
* Thank you!
#+begin_latex
\begin{block}{}
\begin{center}
This spoken tutorial has been produced by the
\textcolor{blue}{FOSSEE} team, which is funded by the
\end{center}
\begin{center}
\textcolor{blue}{National Mission on Education through \\
Information \& Communication Technology \\
MHRD, Govt. of India}.
\end{center}
\end{block}
#+end_latex